Accurate Clock Pendulums

Robert James Matthys

Based on many years of experience in designing and testing different pendulums.

Introduces new materials and modern techniques.

Written in an easy-to-understand manner, with very little mathematics.

Adopts a fresh approach to many old pendulum problems.

Invaluable guide to making a more accurate pendulum or pendulum clock.

Accurate Clock Pendulums

Robert James Matthys

Description

The Shortt clock, made in the 1920's is the most famous accurate clock pendulum ever known, having an accuracy of one second per year when kept at nearly constant temperature. Almost all of a pendulum clock's accuracy resides in its pendulum. If the pendulum is accurate, the clock will be accurate. In this book, the author describes many scientific aspects of pendulum design and operation in simple terms with experimental data, and little mathematics. It has been written, looking at all the different parts and aspects of the pendulum in great detail, chapter by chapter, reflecting the degree of attention necessary for making a pendulum run accurately. The topics covered include the dimensional stability of different pendulum materials, good and poor suspension
spring designs, the design of mechanical joints and clamps, effect of quartz on accuracy, temperature compensation, air drag of different bob shapes and making s sinusoidal electromagnetic drive. One whole chapter is devoted to simple ways of improving the accuracy of ordinary low-cost pendulum clocks, which have a different construction to the more expensive designs of substantially well-made ones. This book will prove invaluable to anyone who wants to know how to make a more accurate pendulum or pendulum clock.

Accurate Clock Pendulums

Robert James Matthys

Table of Contents

General 1. Better accuracy from simple pendulums2. A short history of temperature compensation3. Scaling the size of a pendulum4. Finding a pendulum's axis of rotation5. Does a pendulum's axis of rotation shift with amplitude?6. Some practical properties of quartz7. Putting Q in perspective8. The Allan variance and the root mean square time error9. Transient temperature effects in a pendulum10. Transient response of a pendulum to temperature change11. Dimensional stability of pendulum materials12. Variations on a Riefler bob shape13. Bob shape14. Rate adjustment mechanismsSuspension spring 15. Spring suspensions for accurate pendulums16. James' suspension spring equations17. Barometric compensation with a crossed spring suspension?18. Solid one-piece suspension springs19. Stable connections to a suspension spring20. Stability of suspension spring materialsPendulum rod 21. Pendulum rod materials22. The heat treatment of invar23. The instability of invar24. Position sensitivity along the pendulum rod25. Fasteners for quartz pendulum rods26. Effect of the pendulum rod on QAir and clock case effects 27. Correcting the pendulum's air pressure error28. Pendulum air movement: a failed experiment29. Pendulum air movement: a second try30. Time error due to air pressure variations31. Effect of the clock case walls on a pendulumElectronics 32. An
electronically driven pendulum33. Sinusoidal drive of a pendulum34. Photoelectronics for pendulums35. Check your clock against WWV36. Electronic correction for air pressure variations

Accurate Clock Pendulums

Robert James Matthys

Author Information

Robert J. Matthys was a Senior Research Engineer at Honeywell, Inc., from 1952 to 1987. He has spent thirty-seven years designing a wide variety of hardware and instrumentation in the fields of electronics, optics, acoustics, mechanics, and photography. In addition, he has spent nine years designing and testing pendulums of various kinds, along with their electronic drive systems and servos, both pulsed and continuous sine wave. He lives in Minneapolis, Minnesota.